[PATCH 3/3] KVM: nVMX: Fix vmptrld fail and vmwrite error when L1 goes down

Wanpeng Li
2014-07-17T04:57:45Z

This bug can be trigger by L1 goes down directly w/ enable_shadow_vmcs.

[ 6413.158950] kvm: vmptrld (null)/780000000000 failed
[ 6413.158954] vmwrite error: reg 401e value 4 (err 1)
[ 6413.158957] CPU: 0 PID: 4840 Comm: qemu-system-x86 Tainted: G OE 3.16.0kvm+ #2
[ 6413.158958] Hardware name: Dell Inc. OptiPlex 9020/0DNKMN, BIOS A05 12/05/2013
[ 6413.158959] 0000000000000003 ffff880210c9fb58 ffffffff81741de9 ffff8800d7433f80
[ 6413.158960] ffff880210c9fb68 ffffffffa059fa08 ffff880210c9fb78 ffffffffa05938bf
[ 6413.158962] ffff880210c9fba8 ffffffffa059a97f ffff8800d7433f80 0000000000000003
[ 6413.158963] Call Trace:
[ 6413.158968] [<ffffffff81741de9>] dump_stack+0x45/0x56
[ 6413.158972] [<ffffffffa059fa08>] vmwrite_error+0x2c/0x2e [kvm_intel]
[ 6413.158974] [<ffffffffa05938bf>] vmcs_writel+0x1f/0x30 [kvm_intel]
[ 6413.158976] [<ffffffffa059a97f>] free_nested.part.73+0x5f/0x170 [kvm_intel]
[ 6413.158978] [<ffffffffa059ab13>] vmx_free_vcpu+0x33/0x70 [kvm_intel]
[ 6413.158991] [<ffffffffa0360324>] kvm_arch_vcpu_free+0x44/0x50 [kvm]
[ 6413.158998] [<ffffffffa0360f92>] kvm_arch_destroy_vm+0xf2/0x1f0 [kvm]

Commit 26a865 (KVM: VMX: fix use after free of vmx->loaded_vmcs) fix the use
after free bug by move free_loaded_vmcs() before free_nested(), however, this
lead to free loaded_vmcs->vmcs premature and vmptrld load a NULL pointer during
sync shadow vmcs to vmcs12. In addition, vmwrite which used to disable shadow
vmcs and reset VMCS_LINK_POINTER failed since there is no valid current-VMCS.
This patch fix it by skipping sync shadow vmcs and reset vmcs field for L1
destroy since they will be reinitialized after L1 recreate.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
arch/x86/kvm/vmx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index fbce89e..2b28da7 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6113,9 +6113,9 @@ static void free_nested(struct vcpu_vmx *vmx)
return;
vmx->nested.vmxon = false;
if (vmx->nested.current_vmptr != -1ull) {
- nested_release_vmcs12(vmx);
vmx->nested.current_vmptr = -1ull;
vmx->nested.current_vmcs12 = NULL;
+ nested_release_vmcs12(vmx);
}
if (enable_shadow_vmcs)
free_vmcs(vmx->nested.current_shadow_vmcs);
--
1.9.1